The present invention relates to a motor controller.
To control the speed and torque of a synchronous motor, it is necessary to detect or infer the pole position. By executing current control or voltage control on the basis of the detected pole position, the speed and torque of a synchronous motor can be controlled.
In recent years, a pole position sensorless control system for controlling a synchronous motor without detecting the pole position of the synchronous motor by a position sensor is proposed.
For example, the first control method described in Japanese Application Patent Laid-Open Publication No. Hei 07-245981 and Electric Society, Industry Application Department, National Convention No. 170 in the 8th years of Heisei is a method for applying an alternating voltage and inferring the pole position on the basis of the parallel component and orthogonal component (current component in the rotatory coordinate system) of the motor current for the voltage and the position of the magnetic pole can be detected without using a pole position sensor during stopping or at a low speed.
Further, the second method for superimposing an additional voltage described in Japanese Application Patent Laid-Open Publication No. Hei 11-150983 and Japanese Application Patent Laid-Open Publication No. Hei 11-69884 is a method for realizing no-use of a pole position sensor within the range from low load to high load during stopping or at a low speed by adding an applied voltage so as to prevent magnetic saturation even in the high torque region.
Further, the third control method described in Japanese Application Patent Laid-Open Publication No. Hei 08-205578 is a method for detecting the saliency of a synchronous motor from the mutual relation between the vector of a voltage applied to the synchronous motor by the pulse width control (PWM control) and the ripple component (current difference vector) of the motor current for it. The third method uses a general PWM signal for controlling the voltage of the synchronous motor, so that there is an advantage that there is no need to load an additional signal for detection.
Further, the voltage vector means a voltage having the magnitude and direction decided from a three-phase voltage or d-axis and q-axis voltages. The same may be said with the current vector and hereinafter, each phase voltage as an element or the d-axis and q-axis voltages and the voltage vector as a sum total will be explained appropriately. Further, for the synchronous motor, the pole position of the rotor is to be detected, so that the pole position will be explained hereunder. For a reluctance motor, the specific position of a rotor having saliency is detected.
Further, a control method for detecting the pole position of a rotor in the same way as with the aforementioned method on the basis of the difference in inductance between the q axis and the q axis using the magnetic saturation characteristic of an induction motor is proposed.
Therefore, when the aforementioned is to be described together, the pole position and the specific position of the reluctance motor will be referred to as a rotor position.